Shoot first, ask questions later.
The Shotgun, similar to the M14, uses hit-scanning projectiles. In other words, the projectiles have no travel time. Having a higher base damage than that of the M14, the Shotgun is more lethal at close to mid range, but has a much slower rate of fire than that of the M14. Damage upgrades stack well with the Shotgun, but fire rate upgrades have only a marginal effect. Also, it should be noted that the weapon has no range limitation, however, it does appear that damage decreases to targets at long range due to the pellets being more spread out. This causes the weapon to become slightly less useful against targets that are far away, and is best used in close range combat.